(Adapted from applicant's abstract) Monocular congenital cataracts are generally associated with a poor visual outcome. Although removing a monocular cataract during early infancy improves the visual prognosis in the operated eye, the postoperative corrections of the resultant aphakia continues to be the limiting factor in the visual rehabilitation of these eyes. Correcting the aphakia with contact lenses, epikeratoplasty, or spectacles, magnifies the image in the aphakic eye, thereby creating a disparity in the image sizes between the phakic and aphakic eyes. Infants then suppress the image in the aphakic eye resulting in amblyopia, impaired binocularity and strabismus. This research project is a controlled study using a non-human primate model of a promising new approach to this problem that has the potential to optimize vision in the apakic eye and enhance the potential for binocular vision. Its major objectives are 1) to evaluate the safety and efficacy of intraocular lens implantation in infant; 2) to compare the utility of bifocal with monofocal pseudophakic correction; and 3) to determine whether occlusion therapy is required in monoculary pseudophakic infants in order to achieve good vision in both eyes. The effects of these interventions will be followed regularly in terms of visual acuity, ocular alignment, stereopsis, refractive error, corneal curvature, and axial elongation, and assessed histopathologically after 18 months. In addition, clinical and behavioral results will be compared with morphological changes in the lateral geniculate nucleus and the striate cortex.